Chronic sinusitis is a common pediatric disease; it ranks among the top five infectious diseases of the upper respiratory tract. Its treatment is limited and may due largely in part to a lack of understanding of its pathogenesis. The primary objective of the study was to evaluate the microbiology (through bacteriologic and viral cultures) and local histologic (through maxillary sinus mucosal biopsies) and immunologic (through assays of inflammatory mediators of the maxillary sinus washes) responses in children with chronic sinusitis. The secondary objective was to refine our research methodologies during the course of the study in preparation for a large-scale investigation.